Those may be the official dates, but the cast arrived in Queenstown, NZ at the start of February. The wrap party was around the 18th May but Hugh and others were still filming through June. The Normandy landings were filmed around 11th June. At Comic-Con, in July Hugh claimed to have finished on Wolverine just a few days earlier (could be some exageration there, and he had stopped off in Amsterdam to promote "Australia" on the way).
So 5-6 months.

Hopefully, this production will run smoother and take a shorter time to shoot.